HAL Id: hal-02889192
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Schiff base helicenes
Nicolas Zigon, Mariia Savchuk, Steven Vertueux, N. Avarvari
To cite this version:
Nicolas Zigon, Mariia Savchuk, Steven Vertueux, N. Avarvari. Schiff base helicenes. ISCOM2019, Sep 2019, Tomar, Portugal. 2019. �hal-02889192�
Schiff base helicenes
Nicolas Zigon, Mariia Savchuk, Steven Vertueux, and Narcis Avarvari
Université d'Angers, CNRS UMR 6200, Laboratoire MOLTECH-Anjou, 49045 Angers Cedex, France [email protected]
Goals
Circularly polarized light emitters or complexes displaying magnetochiral dichroism (linking magnetism and chirality) are actively researched species.
1Helicenes form a class of chiral molecules renowned for their intriguing physical properties, particularly their typical helicoidal structure and exceptional chiroptical properties (intense optical activity and circular dichroism). On the other hand, salen ligands are chelating tetradentate Schiff bases whose complexes with metals possess excellent properties in catalysis, luminescence or magnetism, for example.
2The controlled synthesis of chiral magnets as complexes containing both helicene and salen moieties is therefore an important challenge.
3A consistent and systematic study for the synthesis of helicen/salen based derivatives was therefore designed in our group, in order to access compounds displaying magnetochiral dichroism.
X-Ray structure
Structure of the Zn-complex
crystallized in P2
1/c space group
Synthetic methods and characterizations
A synthetic pathway based on a Wittig reaction between a phosphonium ylide and a functionalized aldehyde, followed by a photocyclisation in diluted conditions yields a brominated [4]helicene, whose substitution by cyanide and subsequent reduction to the aldehyde afford the Schiff base precursor.
Reaction with 0.5 equivalent of diamine in MeOH in the presence of a metal provides the desired complexes in good yields (80-90%) for the last step.
Perspectives
A robust synthetic pathway was designed for the synthesis of Schiff base helicenes. Nevertheless, the inherent flexibility of [4]helicene denies it any chirality at room temperature. The synthesis of Schiff base [6]helicene coupled to chiral resolution will provide chiral and conformationnally stable complexes. CD and CPL spectra will be recorded for the complexes, and magnetic optical properties will be measured. Thanks to the versatility of the
organic platform, the extension of this strategy to other metals with magnetic (e.g. Cu
II) or catalytic properties (e.g. Mn
III) will be straightforward.
Bibliography
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2. a) Cozzi P. G. Chem. Soc. Rev., 2004, 33(7), 410–421 ; b) Sammis G. M., Danjo H., Jacobsen E. N. J. Am. Chem. Soc., 2004, 126(32), 9928–9929 ; c) Yoon T. P. Science, 2003, 299(5613), 1691–1693 ; d) Whiteoak C. J., Salassa G., Kleij A. W. Chem. Soc. Rev., 2012, 41(2), 622–631 ; e) Nassief A. R., Abdel-Hafiez M., Hassen A., Khalil A. S. G., Saber M. R. J.
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3. a) Train C., Gheorghe R., Krstic V., Chamoreau L.-M., Ovanesyan N. S., Rikken G. L. J. A., Gruselle M., Verdaguer M., Nat. Mater., 2008, 7 , 729 -734 ; b) Kim S., Kim J., Shin D., Kim Y., Ha Y., Bull. Korean Chem. Soc. 2001, 22, 743-747 ; c) Yu T., Su W., Li W., Hong Z., Hua R., Li B. Thin Solid Films, 2007, 4080–4084 ; d) Barwiolek M., Szlyk E., Muzioła T. M., Lis T., Dalton Trans., 2011, 40, 11012–11022.
X-Ray structure
Structure of the Ni-complex
crystallized in P2
1/c space group.
dNi-Ni = 3.426(4) Å
Formula C44H26N2NiO2 2,5.(CH3OH) Crystal system Monoclinic
Space group P21/c
R1 0.1259
wR2 0.2829
GoF 0.965
M P
250 300 350 400 450 500 550 600 650 700
l (nm) A.U.
rac/trans
Formula C44H28N2ZnO3
.(THF) Crystal system Monoclinic
Space group P21/c
R1 0.0941
wR2 0.2259
GoF 1.035
P
Luminescence properties
Yellow emission
Quantum yields from 3 to 16%
Lifetime from 1.0 to 5.4 ns
Normalized absorption and emission spectra
P
